The present invention relates to a gaseous fuel-air mixture device for internal combustion engines. The device is suitable for use with an engine equipped to run only on gaseous fuel, such as LP gas or on conventional liquid fuel, such as gasoline.
The air pollution problems inherent in the operation of gasoline fueled and diesel-oil fueled internal combustion engines are well known. Although various emission control devices have been used in the past and are presently in use, and although emission control devices are required by federal legislation and regulations to reduce the amount of pollutants discharged in the atmosphere by internal combustion engines, emission control devices are not entirely satisfactory, they are subject to deterioration with the passage of time, and they are often a hindrance preventing the internal combustion engine from operating at best efficiency and at an economical fuel consumption rate.
Natural gas and LP gases, such as propane and butane, have been proposed as a replacement for conventional liquid fuels such as gasoline, for the purpose of reducing atmospheric pollution, reducing consumption of fossil fuels, decreasing the operating costs of internal combustion engines, as compared to the costs of operating on gasoline, and the volume of contaminant emission, as compared to gasoline, without complex emission control devices, or for the purpose of entirely eliminating emission control devices.
LP gases, such as butane and preferably propane, are particularly suitable for fueling internal combustion engines. For example, propane is in a liquid phase under a relatively low pressure at room temperature and requires only thin-walled tanks for safe containment. Many systems using LP gases for fueling internal combustion engines have been proposed and some are presently in use in particular applications such as for service trucks, small tractors, lift trucks and the like, in manufacturing plants and in mines, and for fueling motor vehicles operated by LP gas producers, distributors and dealers.
Vehicles designed to operate on gaseous fuels will be particularly useful to their owners in times when gasoline and diesel fuel become short in supply or are totally unavailable. Other drivers may prefer a vehicle with a dual fuel system, operable on gasoline and gaseous fuel, for example, to protect them in times of shortage.
An example of a dual fuel system for a motor vehicle, where the vehicle can be operated on gaseous fuel or on a conventional liquid fuel such as gasoline is disclosed in co-pending application Ser. No. 138,434, filed Apr. 8, 1980. The invention there disclosed accomplishes the mixing of gaseous fuel and air by means of a proportional mixer where an outer venturi member has an inner smaller diameter venturi member disposed concentrically therein. A gaseous fuel line is connected to an elbow fitting ending in a nozzle disposed concentrically within the inner venturi member and disposed substantially in a plane corresponding to the plane of smallest diameter of the interior of the inner venturi. In such manner, the air flowing into the outer venturi on its way to the intake throat of the carburetor creates a maximum drop of pressure at the outlet of the inner venturi member, thus causing a high velocity flow through the inner venturi. The outlet of the gas supply nozzle being placed on the plane of maximum velocity of the air flow through the inner venturi creates maximum suction of the supplied gas providing thorough mixing of the gas with the entrained air, maximum flow of gas with full throttle opening, minimum flow of gas with fully closed throttle, except for idling adjustment, and no flow of gas upon shutting off the engine, as the pressure of the gas flowing through the low pressure line and the nozzle is lower than atmospheric pressure.
In other heretofore known gaseous fuel systems or dual fuel systems, costly additional mixing systems are required, thus necessitating the replacement of the conventional gasoline carburetor, or, in the alternative, the mounting of a complex gas mixer at the inlet of the carburetor or the mounting of a flange adapter between the carburetor and the engine inlet manifold. What is needed, therefore, is a simple and inexpensive gaseous fuel-air mixture device for gaseous fuels which does not necessitate the replacement of a conventional carburetor.